<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <style>
      /* 填写样式 */
    </style>
  </head>

  <body>
    <!-- 填写标签 -->
    <script type="text/javascript">
      // 填写JavaScript
      const _instanceof = (target, Fn) => {
        let proto = Object.getPrototypeOf(target);
        const fnProto = Object.getPrototypeOf(Fn);
        while (true) {
          if (proto === null) return false;
          if (proto === fnProto) return true;
          proto = Object.getPrototypeOf(proto);
        }
      };
      function a() {}
      let b = new a();
      console.log(_instanceof(a, b));
    </script>
  </body>
</html>
